I use Elmer's as well, usually with bullet-type fishing sinkers. (Fit great in radomes.) I've also used heavy chain as an "emergency" extra weight when the completed model won't quite sit upright--it has the virtue that it will often slide into gaps and recesses (behind inst. panels, for instance) without the need for doing damage to finished construction.
Also--for those who may not have heard--NEVER use CA adhesives with lead or lead-like weights like fishing sinkers. The CA reacts with the metal over time, creating an ongoing "growth" of oxidized material that can and will literally burst the model from the inside. Not what you want to see happen to that much-loved (and sweated over) project.